Method for casting pipes



Feb. 4, 1930. F. HULME METHOD FOR CASTING PIPES Filed Aug. 27, 1925' 2 Sheets-Sheet l INVENTOR ATTORNEY Patented Feb. -4, 1930 UNITED. STATES PATENT OFFICE FRED HULME, OF NEWARK, NEW JERSEY, ASSIGNOR TO JOHN E. HUBBELL, 01'

I NEW YORK, N. Y.

. METHOD FOR CASTING PIPES Application filed August 27, 1925. Serial No. 52,748.

The general object of the present invention is to provide an improved method 'of and apparatus for forming a,hollow metal object by casting it in a mold rotated so that cen- 5 trifugal force will effect or contribute materially to a proper distribution of the metal. A more specific object of the present invention is to make possible the production of centrifugally cast pipes of larger size than have heretofore been made by the centrifugal casting method. A further object of the invention is to provide a practical method of and apparatus for the production of centrifugally cast pipes of large size composed wholly or largely of pearlitic cast iron, though the general features of the invention are useful in the production of castings of other composition and particularly of steel castings.

At the present time centrifugally cast pipes in comparatively small sizes and of good quality, are produced on an extensive commercial scale, but the maximum diameter of the pipes so produced on a commercial scale in this country, is 16 inches. There is an 5 appreciable demand for pipes of much larger diameter, and with my invention it is possible to produce such'pipes of a diameter up to 60 inches or even larger in a relatively inexpensive manner, and of the pearlitic iron a composition which insures the strength,

toughness, and capacity'for machining especially desirable in the case of pipes of large diameter.

My invention is characterized by the use of a relatively massive rotatable metal mold which is at a predetermined temperature appreciably above that of the atmosphere at the beginning of each casting operation therein, and is lined with refractory materlal, so

. 0 as to give it such heat absorbing and dissipating characteristics as are required to cool the casting produced rapidly enough to prevent-the separation of the carbon from the iron which results in the production of gray lining in a mold following the formation of a iron castings on the one hand, and slowlycasting therein'in a simple and relatively inexpensive manner involving the use, in regu-' invention is further characterizedby thenovel' and effective modes in which the pipes are annealed, and are provided with anti-corros'ive coatings.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification, but for a better understanding of the invention, its advantages and specific objects attained withits use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a preferred form of apparatus and preferred mode of operation for carrying out the invention.

Of the drawings Fig. 1 is a diagrammatic plan view of a pipe casting plant;

Fig. 2 is a section on the line 2-2 of Fig. 1;

Fig. 3 is a section on the line 33 of Fig. 1; and

Fig. 4 is a partial section taken similarly to Fig. 3 illustrating means employed for lining the bell end portion of a mold.

In the casting plant somewhat diagrammatically illustrated in the drawings, each pipe formed is cast in a mold A having a refractory lining a, while the mold is supported on and rotated by rolls B, and each mold is lined with a refractory material preparatory to casting a pipe therein while the mold is supported and rotated by rolls 6. C represent track rails or other supporting means adjacent the rolls 6 for the storage of one or more unlined molds. Between the rolls 6 and B are track rails C or other supporting means for the storage of molds A which have been lined and in which the linings are drying. D represents a support receiving each casting when it is discharged so v from the mold in, which it is formed and from which it is ejected as soon as it is cooled sufiiciently. E represents an annealing chamber in which the molds cast are an-- nealed. The molds may be handled in any usual or suitable manner for handling bodies of like weightand form, and ordinar ly each mold after the casting is ejected therefrom, will be transported from its position on the rolls B to the storage station formed by the track rails C by means of an overhead travelling crane which I have not thought it necessary to illustrate. Similarly I have thought it unnecessary to illustrate the means provided for ejecting the finished castings from the molds in which they are formed and for I lacing them on end in the annealing cham- Each mold A is in the form of a one-piece tubular casting. When the pipes cast are each formed with one bell end, each mold A is enlarged at one end both internally and externally to form the bell end portion of the pipe cast therein, and advantageously is internally provided at its enlarged end with a seat for a metal core ring A having a baked core or other suitable lining, for forming the inner and end surfaces of the bellend of the casting formed. Tapered pins or keys A form means for removably securing the core ring A in its seat. -At its opposite end the mold is advantageously provided with a removable annular end piece A which shapes the end surface of the spigot end of the pi 'e cast, and is detachably secured in place y tapered pins or keys A passing through bolts which are secured to the body of 'themold and extend through openings formed for the purpose in the end piece A Intermediate its ends, the mold is provided with two circumferentially extending ribs A which are chilled peripherally to provide suitable tread surfaces for engaging the rolls Bor b, b which the mold is supported and rotate Aside from ground tread-surfaces of the ribs A, and the machined surfaces at the ends of the mold required to seat and secure the core ring A and end piece A in place, each mold-may be an unfinished or unmachinedcasting. The mold is formed with perforations A'. of suitable diameter and suitably spaced for the discharge of gases generated in the casting operation, and each mold may be formed with prickers or internal projections A to assist in holding the lining in place when this seems necessary or desirable.

As shown, there are four supporting rolls B, two engaged by each rib A of the mold, while the latter is in the casting position, Each roll B is formed with a flange B at its inner end whereby any appreciable axial displacement of the mold is prevented; Each of .the two rollsB engaged by one mold tread surface is in axial. alignment with a correspondingroll B engaged by the other tread surface, and each pair of aligned rolls is shown, in a pit lined with concrete or other masonry which is provided to receive the motor B and the pulleys B. As shown, the shaft of the motor B carries a ulley B at each end, and the two pulleys I? are correspondingly displaced longitudinally of the shafts B Each roll B is mounted in a roll supportB having bearings at each side of the roll for the corresponding shaft B The roll su ports B for the two ulleys B engaging t e same tread surface 0 the mold, are movable horizontally toward and away from one another on a supporting beam or rail B", by means of a rotatable roll adjusting shaft 13 having the portions of its length engagin the two roll supports oppositely threade This adjustment of the rolls B is necessary or desirable to secure the proper elevation of .the mold axis, and in particular to adjust the apparatus'to receive molds of different diameter.

In the casting operation, the metal may be put into the rotating mold by mold pouring mechanism generally similar-to that now used with centrifugal piping machines. It is to be noted, however, that because of the preheating of the mold and its relatively slow heat absorbing capacity, the castings produced therein do not set as quickly as they do when made in the pipe casting molds now in use, and in consequence, the mold pouring operation does not needto be ascarefully performed with the present invention as jwiththe pipe castingmachines now in use.

In particular, with my invention, irregularities in the pouring operation are compensated for by the metal distributing effect of centrifugal forceto an extent greater than is possible when the castings'solidify' as rapidly as they do in 'themolds now in commercial use 'for the production of centrifugally cast ipes.

The particular mold pouring mechanism .shown' in the drawings, comprises an elongated trough F mounted on a carriage G, the flanged wheels G of which run on track rails g to move the trough into and out of the mold being poured. While the mold is ordinarily horizontal, the trough is inclined something like three eighths of an inch to the foot, .to cause the metal to run freely to the discharge end F of the trough which, advantageously, is offset at its discharge end F in a known manner to minimize any splashing of the metal discharged. The trough received molten metal through a stationary chute H from a pouring ladle I. Ad

minor fluctuations in that head will produceonly inconsequential variations in the rate of discharge. of metal into the trough F. This facilitates the roper initial distribution of metal longitudinally of the mold, it being understood that the carriage G is moved by its motor G or by other propelling means during the mold pouring operation at the proper rate to effect the uniform withdrawal of the trough from the mold during the period in which the latter is being poured. The ladle I, as shown, may be of any usual or suitable type, and advantageously, as shown, is provided with a bottom outlet I, the flow of the metal through which is controlled by a stopper I moved onto and off' its seat by an operating lever I. The ladle is provided with a bale I suspended as shown from the hook J, of a scale L for weighing the metal charge in the ladle I, the scale itself being I suspended from the hook K of a crane hoist (not shown) or other suitable mechanism for supporting and movingthe ladle.

The rolls b for supporting and rotating a mold in the mold lining operation, may be similar to the rolls B in form, and in the manner in which they are mounted, rotated, and adjusted. The material forming the lining a, may advantageously be mully, i. e., mixture of clay, loam, and sharp sand with sulficient water added to make the mixture quite plastic but a little too stiff to flow freely, so that when put into the mold it will tend to stay where it is put. Advantageously, the thickness of the lining is determined, and its inner surface is smoothed by means of a suitable strike L which in the preferred form shown constitutes the discharge edge of a trough L. The latter after being filled with a suitable amount of mully is moved axially into the mold and then rotated sufficiently to discharge its contents against the rotating mold over the strike edge L. As shown, the trough L is mounted on a carriage M running on track rails m, and is provided with a I bearing for a shaft-like extension L ofthe trough by which the latter is rotatably supported, suitable provisions, (not shown) being made for rotating the shaft L and thereby the trough to discharge the contents of the latter. In Fig. 1, N represents the platform or station at which the trough L is charged with lining material preparatory to lining a mold. The smoothing of the mold lining formed by the strike is insured by the rota-' tion of the mold on the rolls 6. When the pipe mold is formed with an enlarged end for the production of pipes having bell ends, the

lining of the bellend of the mold may be shaped by mounting a removable core member A in the seat provided for the core ring A and workin the lining material into the space between t e core iece and the body of y centrifugal force.-

the mold manually or The core A is replaced, of course, by the core ring A before the mold is poured.

In the regular, normal mode of use of the apparatus contemplated by me, each mold A is moved in regular order from the supporting rails C onto the supporting rolls (1, and is then lined with mull or the like material, while the mold still ho ds the proper amount of residual heat from the previous castin operation therein to properly dry the mully and bake it in place, and to give the mold and its lining the proper temperature to secure the desired rate of cooling for the casting thereafter formed in the mold. The temperature of the mold at the different stages of the operation, and the thickness of the mold and its lining,will vary with conditions of operation, and in particular, with the size and weight of the casting formed. In forming a pipe of say four feet in diameter, and with a wall thickness of about one inch, the mold may well have a metal thickness something like three inches, and the mully lining may well be half or three-quarters of an inch thick. With such sizes and proportions, the temperature of the moldat the time it is lined may well be somethinglike 350 F. and the temperature of the mold and its lining at the time at which the casting is poured therein may well be something like 300 F. It will be understood, of course, that the temperatures and dimensions stated above are given by way of illustration and not by way of preclse limitation, and may be varied in accordance withthe conditions of operation, or as experience makes desirable. After the mold is lined and the linin is dried or baked in place, the lining is preferably faced with blacking, which may be sprayed onto the inner surface of the lining. In starting the plant into operation each mold may be heated before or after it is first lined, as by means of an oil burner inserted in the mold and in regular operation the residual heat of each mold from the previous casting operation may be supplemented by heat from such a burner, if andwhen necessary.

The mold pouring operation may be carried out in a manner analogous to that now position of the casting formed, in large measure depends on the rate at which the mold will absorb heat, and that in turn depends on the heat capacity of the mold, its temperature and its rate of heat dissipation. Primarily, of course, the rate at which the outer surface of the casting formed cools, depends on the rate at which heat is conducted through the lining a, and that rate depends upon the thickness and heat conducting properties of the lining, and on the temperature of the metallic mold body. In proceedlng in accordance with the present invention, I proportion the mold body and its lining, and so regulate the temperature of the mold body that the castings formed will cool rapldly enough to avoid the formation of much, if

any, gray iron, and slowly enough to avoid the formation of more than a small and relatively unimportant amount of white iron and so as to secure a casting composed largely of the desired pearlitic iron composition. To obtain this result, it is necessar of course, to have the molten metal poure of suitable composition which may well be that now employed in making centrifugally cast pipes of the smaller sizes now made. The rate of cooling required for the formation of a high pearlitic iron content in the cast depends somewhat upon the silicon and carbon contents of the metal poured, .and within limits variations in the composition of the iron poured can be compensated for by varying the mold temperature and by varying the mully composition to thereby vary the heat conductivity of the mold lining As soon as the casting is suflici it is ejected from the mold in which it is formed. I have not thought it necessary to' illustrate any mechanism for thus ejecting the casting, as the specific character of the mechanism employed for this purpose forms no part of the present invention, but, on the contrary, may be similar to that now used in the manufacture of centrifugally cast pipes.

The pipes cast ordinarily require annealing or slow cooling to an extent and of a charac ter to eliminate casting strains and to avoid 'strains which might be caused by unduly rapid cooling after the castings are removed from the molds. The annealing operation may well be carried out by transferring-the pipes to a suitable annealing'chamber E, in which they are immersedin a bath of heat insulating material such as Sil-o-cel in granular form. Such material is sufliciently fluid so that when the pipes are placed in the annealing chamber the pipes will settle down in the chamber and will be filled and surrounded by the Sil-o-cel. The pipes are advantageously placed on end in the annealing chamber to avoid their deformation, particularly when of the larger sizes, but-smaller sized pipes may be horizontally disposed in the anneal-- ently cooled,

ing chamber if circumstances make this dein the mo ds in which they are formed, and

before they are passed into the annealin chamber they may advantageously be coate to minimize the possibility of subsequent corrosion. This coating is advantageously formed by dusting the surface of the casting with suitable known agents adapted to form a vitreous or enamel coating when put in dust form on the surfaces of the castings when the latter are sufiiciently hot. This dusting of the coating material onto the castings may advantageously be carried out by means of a pneumatic vibrator or analogous dusting mechanism. Whether or not'the castingsare thus provided with an anti-corrosion coating,

I preferably place them in the annealing chamber before material cooling has occurred.

By proceeding in this manner and employing an annealing chamber and Sil-o-cel therein,

as described. the residual heat in the casting.

when placed in the annealing chamber ordinarily makes it unnecessary to supply adv 'ditional heat in order to secure the proper cooling or annealing efiect desired.-

I am aware that suggestions have heretofore been made for the production of centrifugally cast pipes in metal molds provided with refractory linings, but so far as I am aware, I am the first to provide a suitable method for the commercial production of cast pipes of pearlitic iron composition in refractory lined metal molds, and am the first to provide a practical method of any kind for i the production of large sized pipes of pearlitic iron composition by centrifugal casting,

' Having nowdescribed my invention what I claim as new and desire tosecureby Letters Patent, is:

1. The method of manufacturing large diameter pipes of pearlitic iron compositionwhich comprises lining a mold with plastic refractory material, centrifugally casting the pipes in the mold, and repeating said operations with such frequency'that the heat absorbed by the mold in each casting operation and still retained at the beginning of the subsequentcasting operation will insure a mold temperature sufliciently high .to retard the cooling of the casting formed as required for the formation of a casting of the desired pearli'tic iron composition.

2. The method of manufacturing pipes of pearlitic cast iron composition, which consists in centrifugally casting the pipes in a mold, lining the mold after each casting operation therein with lining material containing suflicientmoisture to make it readily plas tic and repeating the casting and mold lining operations at such intervals that the heat absorbed by the mold in each casting operation will be wholly or in large part sufficient plurality of molds,

to dry and bake the lining next put in place inthe mold and to give the mold and its lining a temperature at the beginning of the following casting operation appreciably abovethat of the atmosphere whereby the cooling of the casting formed is retarded as required for the production of castings of the desired pearlitic iron composition.

3. The method of manufacturing pipes of pearlitic cast iron composition whlch consists in centrifugally casting the pipes in a lining each mold followmg each casting operation therein with refractory material containing sufficient moisture to make the material readily plastic and so regulating the time interval between the formation of successive castings and the number of molds employed that the heat absorbed by each mold in each casting operation will be wholly or in large part sufficient to dry and bake the lining next put in the mold and to give the mold and its lining a temperature at the beginning of the subsequent casting operation appreciably above that of the atmoshere whereby the cooling of the casting ormed is retarded as required for the production of castings of the desired pearlitic iron composition.

4. The method of centrifugally casting pipes in a group of molds in which castings are successively formed in regular repetition which consists in ejecting the casting formed in each mold while it is still very hot, remov' ing the mold to a storing station for initial cooling, then setting the mold into rotation and while in rotation lining it with refractory material moistened to a state of plasticity, then moving the mold to a storing station in which the lining is dried and baked in whole or in lar e part by the retained heat of the mold and then while the mold and the lining is at a temperature appreciably above that of the atmosphere setting the mold into rotation and pouring metal therein to form another casting.

Si ed at Newark, in the county of Essex, and tate of New Jersey, this 1st day of June,

FRED H'ULME. 

